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My new game: Guess how many dB louder the sub(s) is/are to the mains!!!

Flint

Dog Faced Pony Soldier
Superstar
In my efforts to ingratiate myself to the folk in the local audiophile scene, I've been visiting people's listening rooms and auditioning and measuring their systems. To my pleasure, most of them have stereo systems and not surround systems for their primary listening rooms. However, if there is a subwoofer in the room, without fail the gain the sub is so damn high is makes me ache with sorrow and pain.

Today I visited a guy who openly admitted his subwoofer was "hot", but he tended to like it that way. I asked, "How hot is it?" and he, a technologist with a masters in electrical engineering, said it was probably 5 to 6dB hotter than the mains. I was there specifically to test his system so he could have cool charts showing how it performed - he does testing for radio systems so measurements are cool to him.

After listening to most of my auditioning tracks he asked how hot I thought his subwoofer was, and I said 25dB, and he laughed.

I made the typical measurements, and here's what the overall frequency response of his system was in his listening position:
Apogee_Steve_GeneralInRoomResponseWithSub_2019-01-26.jpg

I was pretty right on the money. Between 10Hz and 38Hz the subwoofer is more than 20dB louder than the average response above 100Hz.

This is my new game: "Guess how much louder the subwoofer is than the rest of the speakers".
 

bmwuk

Well-Known Member
I rarely do 2 channel but I know I add somewhere between +3 to +6 db on the sub after running YPAO on my Yamaha. But not sure if that translates the same with 2 channel.
 

Flint

Dog Faced Pony Soldier
Superstar
I asked the question about sub levels on a FB group focuses on high end audio, the same one which very often promotes witch doctor accessories like high end power cables and getting exactly the right external power supply for one's DAC. The responses were interesting.

In most responses people admitted that they tune by ear and feel they have to know the sub is working. Some tune using measurement or calibration tools and openly admit they prefer the subs anywhere from 6dB to 20dB louder than the calibrated "flat" response. A few claimed the ideal is to tune with a SPL Meter on C-Weighting, which results in a subwoofer that is anywhere from 3dB to 9dB louder than the main speakers.

With almost 60 responses, there were only a four or five who's response I could interpret as desiring a flat response in the bass. Including me, that 10% of those willing to respond to my question about subwoofer tuning are setting the goal of a flat(ish) response.
 

Xgm3

Active Member
Every trailer for a Movie or TV show always sounds like they use the same bass track. So I assume that most people think they need a ton of bass for their system to sound good.
 

Dentman

Well-Known Member
My sub is around 2/3db high. I find dead flat to come across as lifeless and without impact. Not always, but for the most part. I'm also finding that I like having my rear chanels on with music. They are very low but on. I'm not sure that its because I like them on or I like what they do to the room acoustics. Either way that's how I enjoy my music the most, in this room as it is right now.
 

Dentman

Well-Known Member
I should also add my love of live music. That "impact" you get from live rock, country, or dance music. Live shows always have boosted lower freq,s/ drums. I like getting that feel at home.
 

Dentman

Well-Known Member
Ok, in the spirit all things the honor system I must admit I was way off. Today I moved some things so I went back and double checked all my speaker levels. Turns out the 2db or so boost on my sub I thought I was set at was way off. I have actually been listening for at least 6 months with my sub set 2 db lower then all my other chanels. I brought it up to dead even. Today.
Another words I'm full of shit. Oh well 1 mistake in a lifetime ain't bad.
 

Dentman

Well-Known Member
Ok, in the spirit all things the honor system I must admit I was way off. Today I moved some things so I went back and double checked all my speaker levels. Turns out the 2db or so boost on my sub I thought I was set at was way off. I have actually been listening for at least 6 months with my sub set 2 db lower then all my other chanels. I brought it up to dead even. Today.
Another words I'm full of shit. Oh well 1 mistake in a lifetime ain't bad.
Actually now this turned out to be wrong also. When Franklin took measurements in my room my sub was around 10db high. Using radio shack spl meter it read my sub was adjusted to flat. I had no idea these meters were so far off when measuring low freq's.
 

Flint

Dog Faced Pony Soldier
Superstar
Actually now this turned out to be wrong also. When Franklin took measurements in my room my sub was around 10db high. Using radio shack spl meter it read my sub was adjusted to flat. I had no idea these meters were so far off when measuring low freq's.
Right, the closest thing to a flat curve from a common SPL meter is based on a C-Weighting on the measurements.

Here's a response chart showing what a C-Weighting is:

C_Weighting.jpg

As you can see, the measured SPL at 20Hz is about 7.5dB below the midrange. So, if you tune your sub to be flat at 20Hz, it will be about 7.5dB too loud. If you try to tune it to 30Hz, then it will be about 3.5dB too loud, and so on.

So, using an SPL meter set to C-Weighting to get what appears to be a flat response between a subwoofer and the main speakers will result in the subwoofer being about 2dB to 8dB louder than the main speakers.
 

Randy

Well-Known Member
Famous
Right, the closest thing to a flat curve from a common SPL meter is based on a C-Weighting on the measurements.

Here's a response chart showing what a C-Weighting is:

View attachment 8807

As you can see, the measured SPL at 20Hz is about 7.5dB below the midrange. So, if you tune your sub to be flat at 20Hz, it will be about 7.5dB too loud. If you try to tune it to 30Hz, then it will be about 3.5dB too loud, and so on.

So, using an SPL meter set to C-Weighting to get what appears to be a flat response between a subwoofer and the main speakers will result in the subwoofer being about 2dB to 8dB louder than the main speakers.

Yes, but all of the calibration disks, along with all of the literature I have read re: system calibration, I have ever seen and used all say to use C-Weighting so most people do just that and don't take into consideration the fact that C-Weighting is not a linear function.

I read in a couple of places online that gave you the differences so you could actually account for C-Weighting and calibrate your sub to flat, but I like most people was too lazy to do it so my subs are, and always have been, set too hot.
 

Flint

Dog Faced Pony Soldier
Superstar
I remember when SVS was getting popular they (and other online sources) made a point of educating users of the lack of low frequency accuracy found in all SPL meters. It is necessary for those meters to filter out the low bass - after all, the low rumble of a delivery truck out on the street, the train going by half a mile away, or one's AC unit would wildly blow the measurement out of whack. The SPL meter takes the sum of all the energy coming into it and determines the SPL, if you don't take the low bass out, the range from 100Hz to 10,000Hz may be averaging about 80dB SPL while some random noise, like a washing machine running the final spin dry cycle, could push the summed SPL to over 90dB. We are trained to ignore common sound we are familiar with when it comes to bass, so road noise or a construction site up the road may not completely ruin our listening experience, but they would ruin calibration with a simple SPL meter if the bass wasn't filtered out of the meter's input.
 
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